Alfalfa Weed Control

Research Update

Kurt Hembree

Farm Advisor, UC Cooperative Extension, Fresno County

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Alfalfa and Forage Meeting

September 18, 2015

Email: kjhembree@ucanr.edu

Office: (559) 241-7520; Cell: (559) 392-6095

Website: cefresno.ucanr.edu

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Weeds and their common impacts:

► Stand development

► Yield

► TDN

► Palatability

► Poisonous

► Off-flavoring

Cheeseweed

Dodder

Fiddleneck

Groundsel

Hairy fleabane

Henbit

Horseweed

Junglerice

Knotweed

Nettle

Sowthistle

Sprangletop

Swinecress

Nutsedge

Yellow foxtail

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

After dormant herbicides applied

Herbicides are commonly applied

during the dormant period:

Weed growth before dormant herbicides applied

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

0

20

40

60

80

100

Rou

ndup

0.5

lb a

i/A

Rou

ndup

1 lb

ai/A

Rou

ndup

2 lb

ai/A

Vel

par+

RU

Vel

par +

Par

Unt

reat

ed

% C

on

tro

l

% Alfalfa % Weeds

Weeds: annual sowthistle, chickweed, burning nettle, malva, annual bluegrass.

Previous work in dormant alfalfa:

Canevari; UCCE Emeritus

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

We began conducting field

trials in 2013 to evaluate the

effect of dormant treatments

of saflufenacil (Sharpen) on

weed control, alfalfa injury,

alfalfa re-growth, and yield.

*Note: Sharpen was not registered in alfalfa in California

at the time of these trials.

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Alfalfa Tolerance to Sharpen

Between Cuttings - 2013

Appl. A = 5/28/13; Sharpen @ 0.0445 lba/A.; All additives @ 1.0% V/V; All treatments AmmoSulfate @ 8.5lb/100gal

TONS/ACRE

MICK CANEVARI

UCCE EMERITUS

SAN JOAQUIN COUNTY

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Results in 2014 (KAC):

0

2

4

6

8

10

7 Dat 14 Dat 30 Dat Harvest

Reg

row

th r

ati

ng

Effect of application timing on alfalfa regrowth

Dec-13 Jan-14 Feb-14

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Results in 2014 (KAC):

0

2

4

6

8

10

7 Dat 14 Dat 30 Dat Harvest

Re

gro

wth

ra

tin

g

Effect of herbicide on alfalfa regrowth

Untreated Sharpen at 2 oz Sharpen at 4 oz Gramoxone at 32 oz

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Alfalfa recovery in 2014 (KAC) (2 weeks after Feb application of Sharpen):

Treated Dec 2013

Treated Jan 2014

Treated Feb 2014

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

No herbicide Sharpen at 2 fl oz/A

Sharpen at 4 fl oz/A Gramoxone Inteon at 32 fl oz/A

Alfalfa recovery in 2014 (KAC) (2 weeks after Feb application):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Treated Dec 2013 Treated Jan 2014 Treated Feb 2014

Alfalfa recovery in 2014 (KAC) (2 weeks before 1st cutting):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Treated Feb 2014

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Alfalfa recovery in 2014 (KAC) (2 weeks before 2nd cutting):

Results 2014 (KAC):

Effect of application timing on alfalfa stem count, height, and yield

Timing

Stem count1

(at harvest)

Harvest2

weight (lbs)

Crop height3

(2nd cutting)

Crop height3

(3rd cutting)

1. A (Dec 13) 43.8 a 41.1 22.8 a 31.5

2. B (Jan 14) 44.1 a 40.8 21.8 a 31.2

3. C (Feb 14) 40.9 b 37.5 20.0 b 30.9

CV (%)

LSD (p=0.05)

8.58

2.65

13.70

n.s.

8.97

1.39

6.26

n.s. 1Number green, productive stems in a 1 ft2 area, and based on three samples per sub-plot. 2Wet weight in pounds, using a Cater plot harvester, swath 6 ft wide by 25 ft long. 3Measured in inches from soil line to top of plant, and based on three samples per sub-plot.

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Results 2014 (KAC):

Effect of herbicide on alfalfa stem count, height, and yield

Herbicide

Rate/A

Stem count2

(at harvest)

Harvest3

weight (lbs)

Crop height4

(2nd cutting)

Crop height4

(3rd cutting)

1. No herbicide 0 44.5 a 43.6 a 22.8 30.1

2. Sharpen1 2 fl oz 44.0 a 39.4 ab 21.2 31.5

3. Sharpen1 4 fl oz 40.1 b 36.7 b 21.1 32.0

4. Gramoxone1 32 fl oz 43.2 ab 39.6 ab 21.0 31.2

CV (%)

LSD (p=0.05)

8.58

3.06

13.70

4.53

8.97

n.s.

6.26

n.s.

1 AMS added at 8.5 lb/100 gal + MSO at 1% v/v. 2Number green, productive stems in a 1 ft2 area, and based on three samples per sub-plot. 3Wet weight in pounds, using a Cater plot harvester, swath 6 ft wide by 25 ft long. 4Measured in inches from soil line to top of plant, and based on three samples per sub-plot.

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Results 2014 (KAC): Effect of app timing and herbicide on weed control and plant composition

Herbicide

Rate/A

Timing

Weed cntrl

30 DAT

Weed cntr

at harvest

Alfalfa

DW (%)

Weed

DW (%)

1. No herbicide 0 A (Dec-13) 0.0 b 0.0 b 96.10 3.90

2. Sharpen 2 fl oz A (Dec-13) 10.0 a 10.0 a 100.00 0.00

3. Sharpen 4 fl oz A (Dec-13) 9.9 a 9.8 a 99.56 0.44

4. Gramoxone 32 fl oz A (Dec-13) 9.9 a 9.8 a 99.83 0.17

5. No herbicide 0 B (Jan-14) 0.0 b 0.0 b 97.47 2.53

6. Sharpen 2 fl oz B (Jan-14) 9.9 a 9.9 a 99.82 0.18

7. Sharpen 4 fl oz B (Jan-14) 9.9 a 9.8 a 99.82 0.18

8. Gramoxone 32 fl oz B (Jan-14) 9.9 a 9.9 a 100.00 0.00

9. No herbicide 0 C (Feb-14) 0.0 b 0.0 b 99.37 0.63

10. Sharpen 2 fl oz C (Feb-14) 10.0 a 10.0 a 100.00 0.00

11. Sharpen 4 fl oz C (Feb-14) 10.0 a 9.9 a 100.00 0.00

12. Gramoxone 32 fl oz C (Feb-14) 9.9 a 9.9 a 99.89 0.11

Statistical notation CV (%)

LSD (p=0.05)

1.02

0.13

2.22

0.28

1.25

n.s.

182.68

n.s. Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Weed control in 2014 (KAC) (after Jan treatment):

No herbicide Sharpen at 2 fl oz/acre

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Herbicide treatments and rates applied on 2/9/2015

Treat Herbicide Rate (product/acre)

1 Untreated 0

2 Sharpen + AMS + MSO 2 fl oz

3 Gramoxone Inteon + AMS + MSO 32 fl oz

4 Velpar + AMS + MSO 32 fl oz

5 Chateau + AMS + MSO 4 oz

6 Sharpen + Prowl H2O + AMS + MSO 2 fl oz + 64.0 fl oz

7 Sharpen + Prowl H2O + Velpar + AMS + MSO 2 fl oz + 64 fl oz + 32 fl oz

8 Sharpen + Velpar + AMS + MSO 2 fl oz + 32 fl oz

9 Chateau + Gramoxone Inteon + AMS + MSO 4 oz + 32 fl oz

AMS = Ammonium sulfate used at 8.5 lbs/100 gal spray volume

MSO = Methylated seed oil (Drexel by BASF) used at 1 % v/v

Alfalfa had 3 to 4” re-growth at time of treatment

Late-dormant Trial 2015 (KAC):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Weed control ratings on 2/23/15 (14 DAT)

Treatment

Shepherd’s-

purse

Chickweed

Swinecress

Horseweed

Prickly

lettuce

Fiddleneck

Annual

bluegrass

Untreated 0.0 c 0.0 b 0.0 c 0.0 e 0.0 c 0.0 b 0.0 c

Sharpen 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Gramoxone Inteon 9.9 ab 10.0 a 9.3 b 8.8 c 10.0 a 10.0 a 10.0 a

Velpar 9.9 ab 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Chateau 9.8 b 10.0 a 9.9 a 5.0 d 9.9 b 10.0 a 9.9 b

Sharpen + Prowl H2O 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Sharpen + Prowl H2O +

Velpar

10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Sharpen + Velpar 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Chateau +

Gramoxone Inteon

9.9 ab 10.0 a 9.9 a 9.6 b 10.0 a 10.0 a 10.0 a

CV (%)

LSD (p=0.05)

0.92

0.12

0.00

0.00

0.92

0.35

2.24

0.26

0.19

0.05

0.00

0.00

0.19

0.05

Weed control based on a visual rating scale of 0-10, where 0 = no control and 10 = 100% or perfect control.

Results in 2015 (KAC):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Weed control ratings on 3/11/15 (28 DAT)

Treatment

Shepherd’s-

purse

Chickweed

Swinecress

Horseweed

Prickly

lettuce

Fiddleneck

Annual

bluegrass

Untreated 0.0 b 0.0 b 0.0 c 0.0 a 0.0 b 0.0 b 0.0 c

Sharpen 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Gramoxone Inteon 9.9 a 10.0 a 9.1 b 8.3 b 10.0 a 10.0 a 10.0 a

Velpar 9.9 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Chateau 9.9 a 10.0 a 9.9 a 3.0 c 10.0 a 10.0 a 9.9 b

Sharpen + Prowl H2O 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Sharpen + Prowl H2O +

Velpar

10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Sharpen + Velpar 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a 10.0 a

Chateau +

Gramoxone Inteon

9.9 a 10.0 a 9.7 a 8.7 b 10.0 a 10.0 a 10.0 a

CV (%)

LSD (p=0.05)

0.76

0.10

0.00

0.00

3.52

0.44

6.26

0.70

0.00

0.00

0.00

0.00

0.38

0.05

Weed control based on a visual rating scale of 0-10, where 0 = no control and 10 = 100% or perfect control.

Results in 2015 (KAC):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

0

2

4

6

8

10

Untreated Sharpen Gramoxone Velpar Chateau Sharpen + Prowl

Sharpen + Prowl + Velpar

Sharpen + Velpar

Chateau + Gramoxone

Inju

ry r

atin

g

Alfalfa injury after late- dormant treatment

14 DAT 28 DAT

Results in 2015 (KAC):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

0

2

4

6

8

10

Untreated Sharpen Gramoxone Velpar Chateau Sharpen + Prowll

Sharpen + Prowl + Velpar

Sharpen + Velpar

Chateau + Gramoxone

Gro

wth

ra

tin

g

Alfalfa re-growth after late- dormant treatment

14 DAT 28 DAT

Results in 2015 (KAC):

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Results in 2015 at 28 DAT (KAC):

UNT Sharpen Sharpen + Prowl H2O Chateau + Gramoxone

Summary

► Sharpen applied alone or mixed with other

herbicides as a dormant treatment can provide

excellent control of tough weeds like sowthistle,

prickly lettuce, horseweed, nettle, and others.

► Sensitivity of alfalfa to Sharpen appears to be

affected by timing of treatment and rate used.

► Delaying treatment with Sharpen until late Jan to

early-Feb may result in lower yields during the first

cutting (at least in the lower SJV).

► Additional work is continuing with this and other

herbicides.

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015

Kurt Hembree, UCCE, Fresno County – Sept 18, 2015